package Map;

import java.util.HashMap;
import java.util.LinkedHashMap;

public class demo03_Linked_hashmap {
    //linkdehashmap extends hashmap
    public static void main(String[] args) {
        HashMap<String,String> map = new LinkedHashMap<>();
        map.put("a","a");
        map.put("c","c");
        map.put("d","d");
        map.put("b","b");
        System.out.println(map);//不重复，有序

    }
}
